<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        console.log(1 + 1); // 2
        console.log('1' + 1); // 11
        console.log('1' - 1); // 0
        
        /* +号可以作为正号解析可以转换为成数字型 */
        console.log(+12); // 12
        console.log(+'123'); // 123
    </script>
</body>
</html>